In virtual machine (e.g., virtual server) environments, a “golden image” is essentially a template that serves as the source of applications, databases, file systems, and other information with which virtual machines are provisioned. Virtual machines can be provisioned by cloning or replicating the golden image. For example, boot volumes for virtual machines can be provisioned by cloning the boot volume of the golden image.
In order to make each virtual machine ready for disaster recovery, the virtual disks of each virtual machine are replicated to remote sites over a wide area network (WAN). After they are created, the remote copies need to be periodically synchronized with the source copy—that is, after they are created, the remote copies need to be kept up-to-date if and when the source copy is modified.
Snapshots are also used to record and preserve the state of a storage device (e.g., a virtual disk) at any given moment. For disaster recovery, the snapshot volumes at the local and remote sites also need to be synchronized. However, standard synchronization mechanisms can be problematic when used for synchronizing snapshots. For example, if standard synchronization mechanisms are applied to snapshots, the copy of a virtual disk at the remote site may end up being larger than the corresponding source (local) version of the virtual disk. Also, synchronizing snapshots using standard synchronization mechanisms can take a relatively long time to complete and/or can consume a relatively large amount of network bandwidth.